package edu.princeton.cs.algs4;

import edu.princeton.cs.stdlib.StdOut;

/*************************************************************************
 *  Compilation:  javac Edge.java
 *  Execution:    java Edge
 *
 *  Immutable weighted edge.
 *
 *************************************************************************/

/**
 * The <tt>Edge</tt> class represents a weighted edge in an undirected graph.
 * <p>
 * For additional documentation, see <a href="/algs4/43mst">Section 4.3</a> of
 * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 */
public class Edge implements Comparable<Edge> {

	private final int v;
	private final int w;
	private final double weight;

	/**
	 * Create an edge between v and w with given weight.
	 */
	public Edge(int v, int w, double weight) {
		this.v = v;
		this.w = w;
		this.weight = weight;
	}

	/**
	 * Return the weight of this edge.
	 */
	public double weight() {
		return weight;
	}

	/**
	 * Return either endpoint of this edge.
	 */
	public int either() {
		return v;
	}

	/**
	 * Return the endpoint of this edge that is different from the given vertex
	 * (unless a self-loop).
	 */
	public int other(int vertex) {
		if (vertex == v)
			return w;
		else if (vertex == w)
			return v;
		else
			throw new RuntimeException("Illegal endpoint");
	}

	/**
	 * Compare edges by weight.
	 */
	public int compareTo(Edge that) {
		if (this.weight() < that.weight())
			return -1;
		else if (this.weight() > that.weight())
			return +1;
		else
			return 0;
	}

	/**
	 * Return a string representation of this edge.
	 */
	public String toString() {
		return String.format("%d-%d %.2f", v, w, weight);
	}

	/**
	 * Test client.
	 */
	public static void main(String[] args) {
		Edge e = new Edge(12, 23, 3.14);
		StdOut.println(e);
	}
}
